300 win mag headspacing

G

gmckinney626

Inactive
Ok, so my first time doing a belted magnum. This is on a 700 .300 WM. I have the go and no-go gauges. I have a Shilen #8 that was threaded and deep chambered at Shilen. I have a thicker recoil lug to install, so obviously, the shoulder has to be set back. The belted gauges have me awefully confused. My concerns are as follows (I'll try to provide as much info as I can):

I'll have to face the barrel to remove the scribings, so I know to account for that with my measurements. I have installed the go gauge and screwed the barrel down onto the action to get a measurement of how far to set back the shoulder. I then removed the go and installed the no-go. Still screws down to the same measurement. As I understand belted magnums, they space off the belt. I've also tried screwing it down on the no-go until it won't close, but then it won't close on the go. I took my measurements on the rim to belt face on both and got .220 on the go and .227-8 on the no-go. The barrel isn't bottoming out on the receiver. So, if I'm getting the same measurement when it's screwed down on either gauge, what am I missing on the cutting that needs to be done?
 
Was your barrell short chambered so a finishing reamer has to be used after fitting it?

I'd ask the barrel's maker how it was chambered. I doubt it was finish chambered at all.
 
You're right that magnum cartridges are headspaced off the rim.

Headspace isn't adjusted by tightening down the barrel. It's done by either pushing a finishing chamber in deeper or if too deep, to shorten the barrel shank.
 
gmckinney626 said:
Ok, so my first time doing a belted magnum. This is on a 700 .300 WM. I have the go and no-go gauges. I have a Shilen #8 that was threaded and deep chambered at Shilen. I have a thicker recoil lug to install, so obviously, the shoulder has to be set back. The belted gauges have me awefully confused. My concerns are as follows (I'll try to provide as much info as I can):

I'll have to face the barrel to remove the scribings, so I know to account for that with my measurements. I have installed the go gauge and screwed the barrel down onto the action to get a measurement of how far to set back the shoulder. I then removed the go and installed the no-go. Still screws down to the same measurement. As I understand belted magnums, they space off the belt. I've also tried screwing it down on the no-go until it won't close, but then it won't close on the go. I took my measurements on the rim to belt face on both and got .220 on the go and .227-8 on the no-go. The barrel isn't bottoming out on the receiver. So, if I'm getting the same measurement when it's screwed down on either gauge, what am I missing on the cutting that needs to be done?
Click to expand...

Are you sure the barrel is not bottoming out on the bolt nose?

Start by screwing the barrel into the receiver with the bolt already locked in battery.
Look at where the barrel stops and measure the gap where the recoil lug would sit.
Run all your measurements against that.

Try out my barrel fitting worksheet to take all your critical measurements and then do your calculated measurements.
www.700barrels.com/stuff/700dimensions.pdf
 
gmckinney626 said:
So Gary, just face the barrel shank to achieve, I speculate, somewhere between .220 and .227 in the seat/ rim ledge?
Click to expand...

That works great IF you know where your boltface datum is and you have a way to take accurate measurements on the barrel.
I made myself several specialized protrusion gauges that will reach around the barrel threads and touch the barrels shoulder and then measure how far a headspace gauge is protruding from the barrel shoulder.
There are commercially made tools like this now, but I made mine many many years ago before they were available off the shelf.
 
Put the barrel behind you, place the receiver in front of you, meaning separate the two, then install the bolt and measure from the front of the receiver ring down to the bolt face with a depth gage or a dial caliper etc, what ever tool you have then (Turn around),place a new unfired, minimum length full length sized store bought round in the chamber and measure case head protrusion from the case head to the mating surface of the barrel.

The Remington 700 HAS A RECOIL LUG, MEASUREMENTS MUST BE TAKEN WITH THE RECOIL LUG INSTALLED. Or the lug thickness can be measured and then subtracted from other measurments etc..when installing the barrel to the receiver the lug must be held om place.

The difference in the two measurements, from the front receiver ring and bolt face and from the protruding case head down the the barrel (to receiver) seating surface determines the length of the chamber from the shoulder of the chamber back to the bolt face.

The bolt face does not have a datum, the bolt face is 'measure to' the shoulder has a datum as in 'measure from' , the datum for the 300 Winchester Magnum is .400 as in a round hole that is 2/5" in diameter. If smiths and reloaders understood the concept they could make their own tools, store bought is OK.

You have head space gage, one a go-gage, the other a no go-gage, the 300 Win Mag head space gages are belt only gages. I want to know the length of the chamber from the shoulder/datum to the bolt facc.

Everyone follows instructions, I remove the belt from a test case to determine the length if the chamber. Those that follow instructions are required to fire form a case to determine the effect the chamber had on the case when fired.

http://www.google.com/search?q=remi...urce=univ&sa=X&ei=9OcjUZDxH4Gi2QXIt4HoAQ&sqi=


F. Guffey
 
Using a new/unfired case that is minimum length/full length sized, a choice, there is more to keep with. It is esier to use the GO-GAGE, for most. When using a new case the person doing the reaming sets the clearence, when using the go-gage no thinking required. I do not shoot gages, I shoot ammo that is minimum length/full length sized ir sized for the chamber.

F. Guffey
 
Quote



"I have a Shilen #8 that was threaded and deep chambered at Shilen"



Yes they do, the instructions that come with some barrels claim all that is required is the seating surfaces to be set back along with the barrel face. But, as indicated, a new thicker recoil lug is going to be used.



F. Guffey
 
Mr Guffey,a problem with using cartridge cases for gages is the cartridge cases vary,and the cartridge case makes a poor gage.

The proper way to set headspace for a belted magnum is off the headspace gage which will then accomodate a maximum loaded cartridge.

It will not do to short chamber to gain a tight headspace at the shoulder of a belted magnum cartridge,as you will not be able to close the bolt on the belt.

The chambering reamer maker puts those dimensions on the reamer.If you have a good reamer,and you put the belt headspace in the right place,then you will be fine if you do not set back the shoulder with the sizing die.


Mr Guffey,I do agree with you about depth mic'ing from the receiver ring to the bolt face..OP,make a drawing,then you won't get confused.
Receiver ring to bolt face,add recoil lug thickness.

The barrel shoulder butts on the recoil lug.Barrel shoulder to the end of the go gage length will end up equalling recoil lug thickness plus receiver ring to bolt face.

If you want to sneak up on it,do the same measurements with the no go gage.Note the difference in length marked on the gages.

So,you can practice by fitting it to the no-go,and if you hit that just right,then you know how much more to take off.If the no-go won't go,and the go does,well,its acceptable.Maybe hand tight on the no go,a feeler gage between the barrel shoulder and recoil lug will tell you some.

Just for fun background,that belt came around from when the British were loading cordite sticks.The load was so many sticks of cordite

Those were loaded into basic,straight brass.Then the brass was easily necked down with the shallow shoulder angle of the H+H cases,the bullet was seated,all was well...except it made for unreliable ignition as the shallow angle was "soft".The belt was added as a good anvil to strike the primer.

But,a belt is so positive,about .005 of clearance was designed in,at minimum,so when Mbogo was going to stomp you,you could count on chambering the round.Reloading was not a consideration.It had to work just once,every time.
 
F. Guffey said:
The Remington 700 HAS A RECOIL LUG, MEASUREMENTS MUST BE TAKEN WITH THE RECOIL LUG INSTALLED. Or the lug thickness can be measured and then subtracted from other measurments etc..when installing the barrel to the receiver the lug must be held om place.

The difference in the two measurements, from the front receiver ring and bolt face and from the protruding case head down the the barrel (to receiver) seating surface determines the length of the chamber from the shoulder of the chamber back to the bolt face.
Click to expand...

HiBC said:
Mr Guffey,I do agree with you about depth mic'ing from the receiver ring to the bolt face..
OP,make a drawing,then you won't get confused.
Receiver ring to bolt face,add recoil lug thickness.
Click to expand...

Did you guys even look at the .PDF file I posted above?
The whole purpose is to log all the dimensions and then determine what the mating dimensions need to be after you account for the clearances you want at the front of the bolt lugs and the bolt nose.
 
Today, 08:24 PM #12
AR15barrels
Member


Join Date: August 23, 2006
Location: Los Angeles, CA
Posts: 32 300 win mag headspacing

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Quote:
Originally Posted by F. Guffey
The Remington 700 HAS A RECOIL LUG, MEASUREMENTS MUST BE TAKEN WITH THE RECOIL LUG INSTALLED. Or the lug thickness can be measured and then subtracted from other measurements etc..when installing the barrel to the receiver the lug must be held in place.

The difference in the two measurements, from the front receiver ring and bolt face and from the protruding case head down the the barrel (to receiver) seating surface determines the length of the chamber from the shoulder of the chamber back to the bolt face.

Quote:
Originally Posted by HiBC
Mr. Guffey,I do agree with you about depth mic'ing from the receiver ring to the bolt face..
OP,make a drawing,then you won't get confused.
Receiver ring to bolt face,add recoil lug thinness.

Did you guys even look at the .PDF file I posted above?
The whole purpose is to log all the dimensions and then determine what the mating dimensions need to be after you account for the clearances you want at the front of the bolt lugs and the bolt nose.

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AR51Barrels, No, I didn’t, I did leave out the part where I say I measure the length of a chamber three different ways, two of those methods do not include a head space gage, with a head space gage the number goes to 4. I measure the length of short chambers in thousandths (.000), then there is the M1917, I measure the length of the 30/06 chamber with a 280 Remington case. Go-gage, I convert go-gages to go-to infinity gages.

Infinity or a more practical .011” longer than a go-gage length chamber.

F. Guffey
 
AR15barrels, I like your .pdf file on doing all the right stuff to fit a barrel to a Rem. 7XX receiver. It reminds me of what one of the service rifle teams (USMC, I think) did back in the '70's fitting 1" to 2" thick recoil lugs on .30 caliber magnum match barrels to Rem 700 receivers in an attempt to eliminate the receivers' twisting in full epoxy bedding contact. The torque of 190 and 200 grain bullets leaving at 3000 fps was/is enough to cause accuracy problems after a couple hundred shots. And those round receivers had no flat surfaces to resist torque like a 4- or 6-flat bolt head does. One of the 'smiths at their rifle shop told me of the issues for determining barrel tenon length based on how thick the recoil lug was. Your instructions made me remember it all over.
 
From post one.


“The barrel isn't bottoming out on the receiver”

Today, 04:12 AM #14
AR15barrels
Member


Join Date: August 23, 2006
Location: Los Angeles, CA
Posts: 33 300 win mag headspacing

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Quote:
Originally Posted by F. Guffey
AR51Barrels, No, I didn’t.

I assume you have no plans to either.



Ar15barrels, you ask if we even looked at the file, I said “No, I didn't”, now you assume I have no plans to look at the file, and the answer is no, I do not plan on looking at the file/link.

If you will notice you have Bart B.s support, what else do you want.


“The barrel isn't bottoming out on the receiver” Back to post #1, I could have informed the original poster he had everything necessary in front him to answer his own question, instead I suggested he separate the two pieces (barrel/receiver).

February 19, 2013, 08:16 PM #11
HiBC
Senior Member


Join Date: November 13, 2006
Posts: 2,933 Mr Guffey,a problem with using cartridge cases for gages is the cartridge cases vary,and the cartridge case makes a poor gage.

The proper way to set headspace for a belted magnum is off the headspace gage which will then accomodate a maximum loaded cartridge.

It will not do to short chamber to gain a tight headspace at the shoulder of a belted magnum cartridge,as you will not be able to close the bolt on the belt.

The chambering reamer maker puts those dimensions on the reamer.If you have a good reamer,and you put the belt headspace in the right place,then you will be fine if you do not set back the shoulder with the sizing die.



Then HiBC informs me I can not do this and or that because etc.. Again, barrels have been shipped with instructions, something like plan A or plan B. I have shared the instructions with individuals on this forum, they have an option to agree and or disagree. The manufacturer of the barrel gives options, I do not argue with them, I am not so conceited to think my plan is the best, I can do the math three different ways, again, I collect datums, I make datums and I purchase datums...cheap. Again, I walk up a table at a gun show and say ‘DATUMS!’ and get three different answers. One, the dealer will say I do not have any datums. Two. someone will ask “WHERE!”. third. “What does a datum look like”.

F. Guffey
 
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F. Guffey said:
“The barrel isn't bottoming out on the receiver” Back to post #1, I could have informed the original poster he had everything necessary in front him to answer his own question, instead I suggested he separate the two pieces (barrel/receiver).
Click to expand...

We don't know if the barrel clears the bolt nose.
Since the barrel stops at the same point with either headspace gauge, we have to consider the possibility that it might not be the gauges that are stopping the barrel.
We might even test to see if the barrel screws in to the same exact point with no headspace gauge at all.
If the barrel is not stopping against the receiver (presume no lug is present) and we determine it is not stopping against the gauges if the barrel stops in the same place with either gauge or even no gauge, then the only thing left that it could be stopping against would be the bolt.

Taking all the three receiver depth measurements on the barrel fitting drawing that I provided would make the problem crystal clear.
 
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AR15barrels
Member


Join Date: August 23, 2006
Location: Los Angeles, CA
Posts: 34 300 win mag headspacing

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Quote:
Originally Posted by F. Guffey
“The barrel isn't bottoming out on the receiver” Back to post #1, I could have informed the original poster he had everything necessary in front him to answer his own question, instead I suggested he separate the two pieces (barrel/receiver).

We don't know if the barrel clears the bolt nose.
Since the barrel stops at the same point with either headspace gauge, we have to consider the possibility that it might not be the gauges that are stopping the barrel.
We might even test to see if the barrel screws in to the same exact point with no headspace gauge at all.
If the barrel is not stopping against the receiver (presume no lug is present) and we determine it is not stopping against the gauges if the barrel stops in the same place with either gauge or even no gauge, then the only thing left that it could be stopping against would be the bolt.

Taking all the three receiver depth measurements on the barrel fitting drawing that I provided would make the problem crystal clear.

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AT15barrels, Would you be happy with the answer ‘yes’?, If so, you should be just as happy with the answer ‘no’.

GMCkenny262 atarted with: “Ok, so my first time doing a belted magnum”, Going from what to 300 Winchester Mag. If you are looking for answers.

We don’t know? I am not the fan of placing an original poster into a dead run by assuming anything. I do not know if the bolt face is designed for a belted magnum, I suggest ‘you suggest’ he remove the bolt then screw the barrel with into the receiver with the recoil lug installed. WHY? “Ok, so my first time doing a belted magnum” THEN! if the barrel is screwed into the receiver with .000 clearance between the front of the receiver and recoil lug I would suggest, you suggest, he install the bolt. If the bolt does not close I suggest 'you suggest’ he screw the barrel out until the bolt closes.

Back to where he has it all together and I suggested he separate the barrel from the receiver, and I said I could accomplish this task three different ways. If he backs the barrel out to close the bolt the gap between the receiver and recoil lug/spacer will indicate if the chamber is short, in thousandths. A feeler gage, companion tool , the companion tool to the press can be used to measure the gap.

Back to the long list of things, methods and techniques that do not work. Before GMCkinney626 uses a head space gage he should start with a 300 WM case that is minimum length/full length sized. Again, after installing/securing the barrel and lug to the receiver, install the bolt, if the bolt closes, remove the bolt and place the empty case into the bolt against the bolt face and chamber the empty round. If the bolt does not close after chambering an empty round screw the barrel out until the bolt closes, after backing the barrel out until the bolt closes measure the gap between the spacer/lug and receiver.

AR15barrels
Member

Join Date: August 23, 2006
Location: Los Angeles, CA
Posts: 34 300 win mag headspacing

--------------------------------------------------------------------------------

Quote:
Originally Posted by F. Guffey
“The barrel isn't bottoming out on the receiver” Back to post #1, I could have informed the original poster he had everything necessary in front him to answer his own question, instead I suggested he separate the two pieces (barrel/receiver).

We don't know if the barrel clears the bolt nose.
AR15barrels
Member

Join Date: August 23, 2006
Location: Los Angeles, CA
Posts: 34 300 win mag headspacing

--------------------------------------------------------------------------------

Quote:
Originally Posted by F. Guffey
“The barrel isn't bottoming out on the receiver” Back to post #1, I could have informed the original poster he had everything necessary in front him to answer his own question, instead I suggested he separate the two pieces (barrel/receiver).

We don't know if the barrel clears the bolt nose.

“The barrel isn't bottoming out on the receiver” “I've also tried screwing it down on the no-go until it won't close” There is go, no and field reject gages. The shortest is the minimum length/full length sized case.

“WE?” I suggest ‘you suggest’ he remove the bolt ‘then’ install the barrel with lug/spacer. Then install the bolt. BUT! FIRST! suggest he take the barrel in one hand and the bolt in the other then place the bolt into the barrel. Again, I check the chamber length of a M1917 30/06 chamber with a 280 Remington case.

Because I do not shoot gages I would have already necked up 10 300 Win Mag cases to 338 and back down to 30 cal.. When necking down I would form a secondary shoulder with various case length.

F. Guffey


I am the fan of knowing case head protrusion and I am the fan of knowing unsupported case head.
 
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What I do for Rem 700 barreling is print out this sketch I made, put it over the lathe, and cross out all the numbers and put in the right numbers for that rifle in red ink.

For my belted magnums; 7mmRM, 300WM, and 338WM, I heaspace at .215", because I can't find any brass more than .215" from the case head to the end of the belt.

Obviously if you are building a rifle for someone else and don't have an understanding with them, you have to headspace at .220" and make it SAAMI kosher, but I know what I want.
 

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Datums

From ASME Y14.5 2009: "Geometric Dimensioning and Tolerancing"

Datum — A theoretically exact point, axis, or plane derived by contact a datum feature; it then becomes the origin from which geometric characteristics are measured.

You cannot buy a datum.Datums are theoretical geometric features,such as planes ,axis,etc.

We can use tools to represent datums ,for example,a granite surface plate may be used to represent a datum plane.Or,as in the Hornady case length caliper gage,the ring privided will rest on the case shoulder to give a useful approximation of the datum .

ASME Y14.5 is THE standard for what terms and definitions apply to engineering drawings.

I am quite comfortable working with it.
 
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